The present invention relates to a new and improved fuel injection installation or fuel injection means for an internal combustion engine, especially a diesel engine.
Generally speaking, the inventive fuel injection installation for an internal combustion engine, especially a diesel engine, is of the type comprising at least one electrically operated fuel injector for each engine cylinder and a common pressure reservoir connected upstream of the fuel injectors and subject to the action of a continuously delivering fuel pump as a function of the engine speed and load. The common pressure reservoir is continuously connected by means of an annular chamber and a throttle to a channel in each fuel injector. Each fuel injector is provided with a solenoid or magnetic valve operable for each fuel injection process and which, when operated, connects the channel to a fuel return pipe and consequently relieves or releases the nozzle needle closing the fuel injection opening of the associated fuel injector and releases the discharge of fuel from a pressure chamber located directly upstream of the fuel injection opening.
In the case of a fuel injection installation or fuel injection means of this type as known from German Patent No. 3,227,742, the annular chamber continuously connected to the pressure reservoir and in which the fuel enters the particular fuel injector is continuously connected via a throttle to the storage chamber or zone directly behind the closable fuel injection opening.
If in the case of a currentless solenoid or magnetic valve, the nozzle needle closes the fuel injection opening then throughout the inner chamber or area of the fuel injector between the nozzle needle seat and the solenoid or magnetic valve body, the set fuel pressure is fully built up and together with a spring presses the nozzle needle against its seat. On operating the solenoid or magnetic valve, the solenoid valve body releases the outflow of fuel from the aforementioned annular chamber via throttles into a fuel return pipe to the fuel tank. The full pressure acting from the storage chamber or zone on the piston of the nozzle needle can now raise the same from the seat against the action of its spring and the pressure drop on the other side of the nozzle needle piston. The fuel previously under high pressure in the storage chamber or zone is relieved and passes out of the fuel injection opening.
As a result, the fuel injection rate rises sharply, reaches its maximum immediately after opening the fuel injection nozzle and then slowly drops, because the fuel flowing into the storage chamber cannot compensate the pressure drop. As soon as the solenoid or magnetic valve becomes currentless again, the pressure above the nozzle needle piston builds up again and, aided by the spring, presses the nozzle needle into its position closing the fuel injection opening, after which the full fuel pressure again builds up in the storage chamber.
This known fuel injection installation results in a good precision of the fuel injection time and the fuel injection quantity, as well as in an economical fuel consumption. However, the course of each individual fuel injection operation is disadvantageous with respect to the emission of pollutants, particularly the discharge of nitrogen oxides. It also leads to a comparatively high combustion noise level. The known fuel injection installation scarcely makes it possible to reduce these disadvantages.